Proteomic evaluation of the non-survival of Anabaena doliolum (Cyanophyta) at elevated temperatures

Abstract

This paper presents proteomic evidence for the non-survival of Anabaena doliolum at elevated temperatures (43°C, 48°C, 53°C and 58°C), when photosystem II (PSII), carbon fixation, ATP and NADPH contents were significantly decreased. A total of 215, 200, 261, 229 and 99 spots were clearly visible in two-dimensional gel electrophoresis (2DE) gels of the cyanobacterium from the control and those subjected to 1 h treatment at the above temperatures, respectively. Proteomic analysis using 2DE, MALDI-TOF MS/MS and reverse transcription polymerase chain reaction of Anabaena exposed to the above temperatures displayed significant and reproducible alterations in 13 proteins homologous to glyceraldehyde-3-phosphate dehydrogenase (GAPDH), fructose-1, 6-bisphosphate aldolase (FBA), fructose-1, 6-bisphosphatase (FBPase), keto-acid reductoisomerase, phycocyanin-α-chain, peroxiredoxin, ATP synthase-β-chain, RNA binding protein, nucleoside diphosphate kinase (NDPK), GroES, phycoerythrocyanin-α-chain, AhpC/TSA family and phycobilisome rod-core linker (PBS-RCL) protein. Except Prx, GroES and ATP synthase-β-chain, other metabolic and oxidative stress proteins were down-regulated at temperatures over 48°C. The down-regulation of FBA, GAPDH, and FBPase beyond 48°C possibly disrupted glycolysis, the pentose phosphate pathway and the Calvin cycle, thereby leading to the death of Anabaena above 48°C. Notwithstanding the above, an appreciable down-regulation of NDPK (involved in protein phosphorylation) and AhpC/TSA (specific scavenger of reactive sulphur species), may lead to loss of signalling and accumulation of reactive sulphur species, respectively, which contribute further to temperature stress. Appreciable induction of heat-shock proteins (HSPs), required for maintenance of metabolic proteins during thermal stress, as well as metabolic proteins up to 48°C and their down-regulation at 53°C and 58°C suggested a close interlinking of these proteins. However, down-regulation of HSP60, HSP26 and HSP 16.6 appears to be responsible for cell death.